Vacuum processing and operating method using a vacuum chamber

ABSTRACT

This invention relates to a vacuum processing apparatus having vacuum processing chambers the insides of which must be dry cleaned, and to a method of operating such an apparatus. When the vacuum processing chambers are dry-cleaned, dummy substrates are transferred into the vacuum processing chamber by substrates conveyor means from dummy substrate storage means which is disposed in the air atmosphere together with storage means for storing substrates to be processed, and the inside of the vacuum processing chamber is dry-cleaned by generating a plasma. The dummy substrate is returned to the dummy substrate storage means after dry cleaning is completed. Accordingly, any specific mechanism for only the cleaning purpose is not necessary and the construction of the apparatus can be made simple. Furthermore, the dummy substrates used for dry cleaning and the substrates to be processed do not coexist, contamination of the substrates to be processed due to dust and remaining gas can be prevented and the production yield can be high.

This application is a Divisional application of application Ser. No.09/177,495, filed Oct. 23, 1998, which is a Continuation application ofapplication Ser. No. 09/061,062, U.S. Pat. No. 5,950,330, filed Apr. 16,1998, which is a Continuation application of application Ser. No.08/882,731, U.S. Pat. No. 5,784,799, filed Jun. 26, 1997, which is aDivisional application of application Ser. No. 08/593,870, U.S. Pat. No.5,661,918, filed Jan. 30, 1996, which is a Continuing application ofapplication Ser. No. 08/443,039, U.S. Pat. No. 5,553,396, filed May 17,1995, which is a Divisional application of application Ser. No.08/302,443, U.S. Pat. No. 5,457,896, filed Sep. 9, 1994, which is aContinuing application of application Ser. No. 08/096,256, U.S. Pat. No.5,349,762, filed Jul. 26, 1993, which is a Continuing application ofapplication Ser. No. 07/751,951, U.S. Pat. No. 5,314,509 filed Aug. 29,1991.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a vacuum processing apparatus and operatingmethod therefor. More specifically, the present invention relates to avacuum processing apparatus having vacuum processing chambers the insideof which must be cleaned, and its operating method.

2. Description of the Prior Art

In a vacuum processing apparatus such as a dry etching apparatus, a CVDapparatus or a sputtering apparatus, a predetermined number ofsubstrates to be treated are stored as one unit (which is generallyreferred to as a "lot") in a substrate cassette and are loaded in theapparatus. The substrates after being processed are likewise stored inthe same unit in the substrate cassette and are recovered. This is anordinary method of operating these apparatuses to improve theproductivity.

In such a vacuum processing apparatus described above, particularly inan apparatus which utilizes a reaction by an active gas, as typified bya dry etching apparatus and a CVD apparatus, reaction products adhere toand are deposited on a vacuum processing chamber with the progress ofprocessing. For this reason, problems such as degradation of vacuumperformance, the increase of dust, the drop of the levels of opticalmonitoring signals occur. To solve these problems, conventionally theinsides of the vacuum processing chambers are cleaned periodically.Cleaning operations include so-called "wet cleaning" which is wiping-offof the adhering matters by use of an organic solvent, etc., and socalled "dry cleaning" in which an active gas or plasma is used fordecomposing adhering matters. Dry cleaning is superior from the aspectof the working factor and efficiency. These features of the dry cleaninghave become essential with the progress in automation of productionlines.

An example of vacuum processing apparatuses having such a dry cleaningfunction is disclosed in Japanese Utility Model Laid-Open No.127125/1988. This apparatus includes a preliminary vacuum chamber forintroducing wafers to be treated into a processing chamber from anatmospheric side to a vacuum side, which is disposed adjacent to theprocessing chamber through a gate valve, dummy wafers are loaded in thepreliminary vacuum chamber and are transferred into the processingchamber by exclusive conveyor means before the processing chamber issubjected to dry cleaning, and the dummy wafer is returned to the vacuumpreparatory chamber by the conveyor means after dry cleaning iscompleted.

SUMMARY OF THE INVENTION

In the prior art technology described above, the structure of the vacuumprocessing apparatus is not much considered. The preliminary vacuumchamber for storing the dummy wafers must have a large capacity, theexclusive conveyor means is necessary for transferring the dummy wafersand thus, the apparatus is complicated in structure.

Dummy wafers used for plasma cleaning are again returned to thepreliminary vacuum chamber and are made to stand by. In this instance,reaction products generated during plasma cleaning and residual gas usedfor plasma cleaning adhere on the used dummy wafers. Thereafter, normalprocessing for wafers is resumed Therefore, the used dummy wafers andunprocessed wafers exist in mixture inside the preliminary vacuumchamber and this state is not desirable from the aspect of contaminationof unprocessed wafers.

The present invention provides a vacuum processing apparatus whichsolves the problems described above, is simple in structure, preventscontamination of unprocessed substrates and accomplishes a highproduction yield. A vacuum processing apparatus having vacuum processingchambers the insides of which are dry-cleaned after substrates to betreated are processed in vacuum is provided with first storage means forstoring substrates to be treated, second storage means for storing dummysubstrates, the first and second storage means being disposed in theair, conveyor means for transferring the substrates to be processedbetween the first storage means and the vacuum processing chambers andfor transferring the dummy substrates between the second storage meansand the vacuum processing chambers, and control means for controllingthe conveyor means so as to transfer the dummy substrates between thesecond storage means and the vacuum processing chambers before and afterdry cleaning of the vacuum processing chambers. A method of operating avacuum processing apparatus having vacuum processing chambers theinsides of which are dry-cleaned after substrates to be processed areprocessed in vacuum comprises the steps of disposing first storage meansfor storing the substrates to be processed together with second storagemeans for storing dummy substrates in the air atmosphere, transferringthe substrates to be processed between the first storage means and thevacuum processing chambers and vacuum-processing the substrates to beprocessed, and transferring the dummy substrates between the secondstorage means and the vacuum processing chambers before and afterdry-cleaning of the vacuum processing chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a dry etching apparatus as an embodiment of avacuum processing apparatus in accordance with the present invention;and

FIG. 2 is a vertical sectional view taken along line 1--1 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As substrates to be processed are processed in a vacuum processingapparatus, reaction products adhere to and are deposited in vacuumprocessing chambers. The reaction products adhering to and deposited inthe vacuum processing chambers are removed by disposing dummy wafersinside the vacuum processing chambers and by conducting dry-cleaning. Tocarry out dry cleaning, the timings of dry cleaning of the vacuumprocessing chambers are determined and during or after the processing ofa predetermined number of substrates to be processed, dummy substratesare conveyed by substrate conveyor means from dummy substrate storagemeans disposed in the air atmosphere together with processed substratestorage means, and are then disposed inside the vacuum processingchambers. After the dummy substrates are thus disposed, a plasma isgenerated inside each of the vacuum processing chambers to executedry-cleaning inside the vacuum processing chamber. After dry-cleaninginside the vacuum processing chambers is completed, the dummy substratesare returned from the vacuum processing chambers to the dummy substratestorage means by the substrate conveyor means. In this manner, apreliminary vacuum chamber and an exclusive transfer mechanism bothnecessary in prior art techniques become unnecessary, and the apparatusstructure gets simplified. The dummy substrates used for thedry-cleaning and the substrates to be processed do not co-exist insidethe same chamber, so that contamination of substrates to be processeddue to dust and remaining gas is prevented and a high production yieldcan be achieved.

Hereinafter, an embodiment of the present invention will be explainedwith reference to FIGS. 1 and 2.

FIGS. 1 and 2 show a vacuum processing apparatus of the presentinvention which is, in this case, a dry-etching apparatus for etchingwafers, i.e., substrates to be processed by plasma.

Cassette tables 2a to 2c are disposed in an L-shape in this case inpositions such that they can be loaded into and unloaded from theapparatus without changing their positions and postures. In other words,the cassettes 1a to 1c are fixed always in predetermined positions on asubstantially horizontal plane, while the cassette tables 2a and 2b aredisposed adjacent to and in parallel with each other on one of the sidesof the L-shape. The cassette table 2c is disposed on the other side ofthe L-shape. The cassettes 1a and 1b are for storing unprocessed wafersand for recovering the processed wafers. They can store a plurality(usually 25) of wafers 20 as the substrates to be treated. The cassette1c in this case is for storing the dummy wafers for effectingdry-cleaning using plasma (hereinafter referred to as "plasma-cleaning")and recovering the dummy wafers after plasma-cleaning. It can store aplurality of (usually twenty-five pieces) dummy wafers 30.

A load lock chamber 5 and unload lock chamber 6 are so disposed as toface the cassette tables 2a and 2b, and a conveyor 13 is disposedbetween the cassette tables 2a, 2b and the load lock chamber 5 and theunload lock chamber 6. The load lock chamber 5 is equipped with anevacuating device 3 and a gas introduction device 4, and can loadunprocessed wafers in the vacuum apparatus through a gate valve 12a. Theunload lock chamber 6 is similarly equipped with the evacuating device 3and the gas introduction device 4, and can take out processed wafers tothe atmosphere through a gate valve 12d. The conveyor 13 is equippedwith a robot having X, Y, Z and 6 axes, which operates so as to deliverand receive the wafers 20 between the cassettes 1a, 1b and the load lockand unload lock chambers 5 and 6 and the dummy wafers 30 between thecassette 1c and the load lock and unload lock chambers 5 and 6.

The load lock chamber 5 and the unload lock chamber 6 are connected to atransfer chamber 16 through the gate valves 12b and 12c. The transferchamber 16 is rectangular, in this case, and etching chambers 11a, 11band 11c are disposed on the three side walls of the transfer chamber 16through gate valves 15a, 15b and 15c, respectively. A conveyor 14capable of delivering the wafers 20 or the dummy wafers 30 from the loadlock chamber 5 to the etching chambers 11a, 11b, 11c and of deliveringthem from the chambers 11a, 11b, 11c to the unload lock chamber 6 isdisposed inside the transfer chamber 16. The transfer chamber 16 isequipped with an evacuating device 17 capable of independent evacuation.

The etching chambers 11a, 11b, 11c have the same structure and can makethe same processing. The explanation will be given on the etchingchamber 11b by way of example. The etching chamber 11b has a sampletable 8b for placing the wafers 20 thereon, and a discharge chamber isso provided as to define a discharge portion 7b above the sample table8b. The etching chamber 11b includes a gas introduction device 10b forintroducing a processing gas in the discharge portion 7b and anevacuating device 9b for decreasing the internal pressure of the etchingchamber 11b to a predetermined pressure. The etching chamber 11b furtherincludes generation means for generating a microwave and a magneticfield for converting processing gas in the discharge portion 7b toplasma.

A sensor 18 for measuring the intensity of plasma light is disposed atan upper part of the etching chamber. The measured value of the sensor13 is inputted to a controller 19. The controller 19 compares themeasured value from the sensor 18 with a predetermined one anddetermines the timing of cleaning inside the etching chamber. Thecontroller 19 controls the conveyors 13 and 14 to control the transferof the dummy wafers 30 between the cassette 1c and the etching chambers11a to 11c.

In a vacuum processing apparatus having the construction describedabove, the cassettes 1a, 1b storing unprocessed wafers are first placedonto the cassette tables 2a, 2b by a line transfer robot which operateson the basis of the data sent from a host control apparatus, or by anoperator. On the other hand, the cassette 1c storing the dummy wafers isplaced on the cassette table 2c. The vacuum processing apparatusexecutes the wafer processing or plasma cleaning on the basis ofrecognition by itself of the production data provided on the cassettes1a to 1c, of the data sent from the host control apparatus, or of thecommand inputted by an operator.

For instance, the wafers 20 are sequentially loaded in the order promabove into the etching chambers 11a, 11b, 11c by the conveyors 13 and14, and are etched. The etched wafers are stored in their originalpositions inside the cassette 1a by the conveyors 14 and 13. In thiscase, from the start to the end of the operation, without changing theposition and posture of the cassettes, the unprocessed wafers are takenout from the cassettes and are returned in their original positionswhere the wafers have been stored, and are stored there. In this manner,the apparatus can easily cope with automation of the production line,contamination of the wafers due to dust can be reduced and highproduction efficiency and high production yield can thus beaccomplished.

As etching is repeated, the reaction products adhere to and aredeposited on the inner wall of the etching chambers 11a to 11c.Therefore, the original state must be recovered by removing the adheringmatters by plasma cleaning. The controller 19 judges the timing of thisplasma cleaning. In this case, a portion through which the plasma lightpasses is provided in each of the etching chambers 11a to 11c. Thesensor 18 measures the intensity of the plasma light passing throughthis portion and when the measured value reaches a predetermined one,the start timing of plasma cleaning is judged. Alternatively, the timingof plasma cleaning may be judged by counting the number of wafersprocessed in each etching chamber by the controller 19 and judging thetiming when this value reaches a predetermined value. The actual timingof plasma cleaning that is carried out may be during a processing of apredetermined number of wafers in the cassette 1a or 1b, after theprocessing of all the wafers 20 in a cassette is completed and beforethe processing of wafers in the next cassette.

Plasma cleaning is carried out in the following sequence. In this case,the explanation will be given about a case where the etching chambers11a to 11c are subjected to plasma cleaning by using three dummy wafers30 among the dummy wafers 30 (twenty-five dummy wafers are stored inthis case) stored in the cassette 1c.

Dummy wafers 30 which are stored in the cassette ic and are not used yetor can be used because the number of times of use for plasma cleaning isbelow a predetermined one are drawn by the conveyor 13. At this time,dummy wafers 30 stored in any position in the cassette 1c may be usedbut in this case, the position numbers of the dummy wafers in thecassette and their number of times of use are stored in the controller19, and accordingly dummy wafers having smaller numbers of times of useare drawn preferentially. Then, the dummy wafers 30 are loaded in theload lock chamber 5 disposed on the opposite side to the cassette 1a bythe conveyor 13 through the gate valve 12a in the same way as thetransfer at the time of etching of wafers 20. After the gate valve 12ais closed, the load lock chamber 5 is evacuated to a predeterminedpressure by the vacuum exhaust device 3 and then the gate valves 12b and15a are opened. The dummy wafers 30 are transferred by the conveyor 14from the load lock chamber 5 to the etching chamber 11a through thetransfer chamber 16 and are placed on the sample table 8a. After thegate valve 15a is closed, plasma cleaning is carried out in the etchingchamber 11a in which the dummy wafers 30 are disposed, under apredetermined condition.

In the interim, the gate valves 12a, 12b are closed and the pressure ofthe load lock chamber 5 is returned to the atmospheric pressure by thegas introduction device 4. Next, the gate valve 12a is opened and thesecond dummy wafer 30 is loaded in the load lock chamber 5 by theconveyor 13 in the same way as the first dummy wafer 30, and evacuationis effected again by the evacuating device 3 to a predetermined pressureafter closing the gate valve 12a. Thereafter, the gate valves 12b and15b are opened and the second dummy wafer 30 is transferred from theload lock chamber 5 to the etching chamber 11b through the transferchamber 16 by the conveyor 14. Plasma cleaning is started after the gatevalve 15b is closed.

In the interim, the third dummy wafer 30 is transferred into the etchingchamber 11c in the same way as the second dummy wafer 30 and plasmacleaning is carried out.

After plasma cleaning is completed in the etching chamber 11a in whichthe first dummy wafer 20 is placed, the gate valves 15a and 12c areopened. The used dummy wafer 30 is transferred from the etching chamber11a to the unload lock chamber 6 by the conveyor 14. Then, the gatevalve 12c is closed. After the pressure of the unload lock chamber 6 isreturned to the atmospheric pressure by the gas introduction device 4,the gate valve 12d is opened. The used dummy wafer 30 transferred to theunload lock chamber 6 is taken out in the air by the conveyor 13 throughthe gate valve 12d and is returned to its original position in thecassette 1c in which it is stored at the start.

When plasma cleaning of the etching chambers 11b and 11c is completed,the second and third dummy wafers 20 are returned to their originalpositions in the cassette 1c.

In this way, the used dummy wafers 30 are returned to their originalpositions in the cassette 1c and the dummy wafers 30 are always stockedin the cassette 1c. When all the dummy wafers 30 in the cassette 1c areused for plasma cleaning or when the numbers of times of use of thewafers 30 reach the predetermined ones after the repetition of use, thedummy wafers 30 are replaced as a whole together with the cassette 1c.The timing of this replacement of the cassette is managed by thecontroller 19 and the replacement is instructed to the host controlapparatus for controlling the line transfer robot or to the operator.

Although the explanation given above deals with the case where theetching chambers 11a to 11c are continuously plasma-cleaned by the useof three dummy wafers 30 among the dummy wafers 30 in the cassette 1c,other processing methods may be employed, as well.

For example, the etching chambers 11a to 11c are sequentiallyplasma-cleaned by the use of one dummy wafer 30. In the case of suchplasma cleaning, unprocessed wafers 20 can be etched in etching chambersother than the one subjected to plasma cleaning, and plasma cleaning canthus be carried out without interrupting etching.

If the processing chambers are different, for example, there are anetching chamber, a post-processing chamber and a film-formation chamber,and wafers are sequentially processed while passing through each ofthese processing chambers, each of the processing chambers can besubjected appropriately to plasma cleaning by sending dummy wafers 30during the processing of the wafers 20 which are stored in the cassette1a or 2a and drawn and sent sequentially, by passing merely the dummywafers 30 through the processing chambers for which plasma cleaning isnot necessary, and by executing plasma cleaning only when the dummywafers 30 reach the processing chambers which need plasma cleaning.

According to the embodiment described above, the cassette storing thedummy wafers and the cassettes storing the wafers to be processed aredisposed together in the air, the dummy wafers are loaded from thecassette into the apparatus by the same conveyor as the conveyor fortransferring the wafers, at the time of cleaning, and the used dummywafers are returned to their original positions in the cassette. In thisway, a mechanism for conducting exclusively plasma cleaning need not beprovided, and the construction of the apparatus can be simplified. It isnot necessary to handle plasma cleaning as a particular processingsequence, but the plasma cleaning can be incorporated in an ordinaryetching processing and can be carried out efficiently in a series ofoperations.

The dummy wafers used for plasma cleaning are returned to their originalpositions in the cassette placed in the air. Accordingly, the used dummywafers and the wafers before and after processing do not exist mixedlyin the vacuum chamber, so that contamination of wafers due to dust andremaining gas does not occur unlike conventional apparatuses.

The used dummy wafers are returned to their original positions in thecassette and the numbers of times of their use is managed. Accordingly,it is possible to prevent the confusion of the used dummy wafers withthe unused dummy wafers and the confusion of the dummy wafers havingsmall numbers of times of use with the dummy wafers having large numbersof times of use. For these reasons, the dummy wafers can be usedeffectively without any problem when plasma cleaning is carried out.

Furthermore, in accordance with the present invention, the apparatus canhave a plurality of processing chambers and can transfer wafers anddummy wafers by the same conveyor. Since plasma cleaning can be carriedout by managing the timing of cleaning of each processing chamber by thecontroller, the cleaning cycle can be set arbitrarily, dry cleaning canbe carried out without interrupting the flow of the processing, theprocessing can be efficiently made and the productivity can be improved.

As described above, according to the present invention, there areeffects that the construction of the apparatus is simple, the substratesto be processed are free from contamination and the production yield ishigh.

What is claimed is:
 1. A method of transferring a cassette containing asample, comprising the steps of:transferring the cassette to a cassettetable, said cassette table being disposed in the vicinity of a vacuumprocessing apparatus and being disposed under a cassette transferringatmospheric pressure; placing the transferred cassette on said cassettetable; removing the placed cassette from said cassette table; andtransferring the removed cassette to another position.
 2. A method oftransferring a cassette containing a sample according to claim 1,wherein the sample is a semiconductor wafer.
 3. A method of transferringa cassette containing a sample according to claim 1, wherein the step oftransferring the cassette to the cassette table includes transferringthe cassette to a position corresponding to the location of the cassettetable.
 4. A method of transferring a wafer storing structure containinga semiconductor wafer, comprising the steps of:transferring the waferstoring structure to a wafer storing structure table, said wafer storingstructure table being in the vicinity of a vacuum processing apparatusand being disposed under a wafer storing structure transferringatmospheric pressure; placing the transferred wafer storing structure onsaid wafer storing structure table; removing the placed wafer storingstructure from said wafer storing structure table; and transferring theremoved wafer storing structure to another position.
 5. A method oftransferring a wafer storing structure containing a semiconductor waferaccording to claim 4, wherein the step of transferring the wafer storingstructure to the wafer storing structure table includes transferring thewafer storing structure to a position corresponding to the location ofthe wafer storing structure table.
 6. A method of transferring acassette containing a sample, comprising the steps of:transferring thecassette to a cassette table, the cassette table being in the vicinityof a vacuum processing apparatus and being disposed under a cassettetransferring atmospheric pressure; placing the transferred cassette onsaid cassette table, wherein in placing the transferred cassette, atransferring state of said cassette is maintained without changing anorientation of the placed cassette; removing the placed cassette fromsaid cassette table; and transferring the removed cassette to anotherposition.
 7. A method of transferring a cassette containing a sampleaccording to claim 6, wherein the sample is a semiconductor wafer.
 8. Amethod of transferring a cassette containing a sample according to claim6, wherein the step of transferring the cassette to the cassette tableincludes transferring the cassette to a position corresponding to thecassette table.
 9. A method of transferring a wafer storing structurecontaining a semiconductor wafer, comprising the steps of:transferringthe wafer storing structure to a wafer storing structure table, saidwafer storing structure table being in the vicinity of a vacuumprocessing apparatus and being disposed under a wafer storing structuretransferring atmospheric pressure; placing the transferred wafer storingstructure on said wafer storing structure table, wherein in placing thetransferred wafer storing structure, a transferring state of said waferstoring structure is maintained without changing an orientation of theplaced wafer storing structure; removing the placed wafer storingstructure from said wafer storing structure table; and transferring theremoved wafer storing structure to another position.
 10. A method oftransferring a wafer storing structure containing a semiconductor waferaccording to claim 9, wherein the step of transferring the wafer storingstructure to the wafer storing structure table includes transferring thewafer storing structure to a position corresponding to the location ofthe wafer storing structure table.